Svelte 的核心是一个强大的反应系统，用于使 DOM 与你的应用状态保持同步 - 例如，响应事件。

¥At the heart of Svelte is a powerful system of reactivity for keeping the DOM in sync with your application state — for example, in response to an event.

通过将值封装在 $state(...) 中使 count 声明具有响应性：

¥Make the count declaration reactive by wrapping the value with $state(...):

let count = $state(0);

这称为符文，你可以通过它告诉 Svelte count 不是普通变量。符文看起来像函数，但它们是语言本身的一部分。

¥This is called a rune, and it’s how you tell Svelte that count isn’t an ordinary variable. Runes look like functions, but they’re not — when you use Svelte, they’re part of the language itself.

剩下的就是实现 increment：

¥All that’s left is to implement increment:

function increment() {
	count += 1;
}